Novelamphiphilic Hollow Nickel-based Alloy Nanocatalysts For The Aqueous-phase Catalysis Of α-pinene/rosin Hydrogenation Reaction

Turpentine is one of the largest biomass petroleum resources in the world,and from which two products of rosin and turpentine can be obtained by distillation.α-Pinene and rosin acid are the major ingredients of turpentine and rosin,respectively,which afford cis-pinane and hydrogenated rosin by hydrogenation,providing important intermediates for the synthesis of fine chemicals.Although the current catalysts used for the hydrogenation ofα-pinene and rosin have many advantages,the harsh reaction conditions and the non-renewability of the catalysts are major concerns.Water is an environmentally friendly green solvent with merits of widely exist and cheap,gaining great attractions being used as a reaction medium for multiphase catalytic reactions.However,most of the previous developed catalysts are insoluble and reprone to aggregation in water,unflavoring the contact with the substrate.Therefore,in this work,two amphiphilic mesoporous hollow nanocatalysts are prepared and used for the hydrogenation ofα-pinene/rosin in aqueous condition.N-doped hollow mesoporous nanomaterial NHMC@m Si O₂is prepared by domain-limited carbonisation using resorcinol and formaldehyde as carbon precursors,ethylenediamine（EDA）as a nitrogen source and tetraethyl orthosilicate（TEOS）as a silicon source.Then,the catalyst Ru-Ni/NHMC@m Si O₂is prepared by the hydrogen reduction of the complex of metal Ru,Ni and NHMC@m Si O₂,which is characterized by SEM,TEM,XPS,XRD measurements.With this catalyst,the hydrogenation conditions ofα-pinene and rosin in aqueous phase are screened.In the hydrogenation ofα-pinene,under 100℃and 1.0 MPa H₂,the conversion ofα-pinene reaches 98.7%with the selectivity of cis-pinene up to 96.9%in 3 h.The catalyst could be recycled for more than 7 times without any significant decrease in catalytic activity.In the hydrogenation of rosin,under 140℃and 3.0 MPa H₂,the conversion reaches 98.5%with the selectivity of tetrahydroabietic acid and dehydroabietic acid in 32.5%and1.1%,respectively.The catalyst could be repeatedly used over 6 times without any significant decrease in catalytic performance.A new carrier material NPHMC@m Si O₂containing weak acid sites is prepared by pyrolyed phosphorylation by using sodium hypophosphite as the phosphorus source.The Ni-Co/NPHMC@m Si O₂catalyst is prepared by hydrogen reduction of the complex of metal Ni,Co and NPHMC@m Si O₂,which is characterized by SEM,TEM,XPS,XRD and NH₃-TPD.With this catalyst,the hydrogenation conditions ofα-pinene and rosin in aqueous phase are screened.In the hydrogenation ofα-pinene,under130℃and 2 MPa H₂,the conversion reaches 95.6%with the selectivity of cis-pinane in 92.5%in 3 h.The catalyst could be recycled 6 times without any significant decrease in its catalytic activity.In the hydrogenation of rosin,under 130℃and 4MPa,the conversion reaches 98.1%with the selectivity of tetrahydroabietic acid and dehydroabietic acid in 33.7%and 2.1%in 4 h,which meet the requirements for the production of high quality rosin.The catalyst could be used repeatedly over 5 times without any significant decrease in performance.In this paper,two amphiphilic alloy nanocatalysts are prepared by hydrogen reduction.The excellent reactivities of the catalysts in the hydrogenation ofα-pinene/rosin in aqueous condition could be attributed to the large lipophilic cavity structure of the materials,which facilitates the mass transfer and enrichment of the substrate.The presence of a hydrophilic shell also allows them to be well dispersed in water,increasing their contact area with the substrate and thus improving the efficiency of the reaction.The hydrogen reduction preparation of the catalyst is safe and results in a high hydrogen utilization.The high activity and stability of alloy catalysts also results from the strong interaction between the metal and the carrier and the synergistic interaction among the metals.This work provides new ways for the development of environmentally friendly heterogeneous catalysts for hydrogenation reactions.